Messages in this thread | | | Subject | Re: [patch 3/3] nohz/s390: fix arch_needs_cpu() return value on offline cpus | From | Peter Zijlstra <> | Date | Fri, 26 Nov 2010 13:14:07 +0100 |
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On Fri, 2010-11-26 at 13:01 +0100, Heiko Carstens wrote: > plain text document attachment (003_arch_needs_cpu.diff) > From: Heiko Carstens <heiko.carstens@de.ibm.com> > > This fixes the same problem as described in the patch "nohz: fix > printk_needs_cpu() return value on offline cpus" for the arch_needs_cpu() > primitive. > This specific bug was indrocuded with 3c5d92a0 "nohz: Introduce arch_needs_cpu". > > In this case a cpu hotplug notifier is used to fix the issue in order to keep > the normal/fast path small. All we need to do is to clear the condition that > makes arch_needs_cpu() return 1 since it is just a performance improvement which > is supposed to keep the local tick running for a short period if a cpu goes > idle. Nothing special needs to be done except for clearing the condition. > > Cc: stable@kernel.org > Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
OK, and s390 seems to be the only architecture making use of that interface.
Did you audit all the other *_needs_cpu() interfaces for this same problem?
Anyway,
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Will you take this through the s390?
> --- > arch/s390/kernel/vtime.c | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > --- a/arch/s390/kernel/vtime.c > +++ b/arch/s390/kernel/vtime.c > @@ -19,6 +19,7 @@ > #include <linux/kernel_stat.h> > #include <linux/rcupdate.h> > #include <linux/posix-timers.h> > +#include <linux/cpu.h> > > #include <asm/s390_ext.h> > #include <asm/timer.h> > @@ -566,6 +567,23 @@ void init_cpu_vtimer(void) > __ctl_set_bit(0,10); > } > > +static int __cpuinit s390_nohz_notify(struct notifier_block *self, > + unsigned long action, void *hcpu) > +{ > + struct s390_idle_data *idle; > + long cpu = (long) hcpu; > + > + idle = &per_cpu(s390_idle, cpu); > + switch (action) { > + case CPU_DYING: > + case CPU_DYING_FROZEN: > + idle->nohz_delay = 0; > + default: > + break; > + } > + return NOTIFY_OK; > +} > + > void __init vtime_init(void) > { > /* request the cpu timer external interrupt */ > @@ -574,5 +592,6 @@ void __init vtime_init(void) > > /* Enable cpu timer interrupts on the boot cpu. */ > init_cpu_vtimer(); > + cpu_notifier(s390_nohz_notify, 0); > } > >
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